Pneumatic tires

ABSTRACT

Pneumatic tires reinforced with a carcass and a breaker, said carcass being composed of polyester fiber or 6,6-nylon fiber cord layer and said breaker being composed of aromatic polyamide fiber cord layer having particularly defined tenacity, initial modulus and twisting coefficients of cable twist and ply twist and the rubber to embed the breaker having 300 percent modulus of 130 250 Kg/cm2.

Unite States Patent 11 1 Takemura et al.

[451 Dec.3,1974

[ 1 PNEUMATIC TIRES [75] Inventors: Satoshi Takemura; Katsuyuki Harakon; Mitsuaki Maeda; Noboru Sakai; Etsuko Hamano, all of Tokyo, Japan [73] Assignee: Bridgestone Tire Company Limited,

Tokyo, Japan [22] Filed: Dec. 21, 1973 [21] Appl. No.: 427,169

[30] Foreign Application Priority Data Dec. 29, 1972 Japan .l 48 3221 [52] U.S. Cl. 152/361 R, 152/330 R, 152/357 [51] Int. Cl. 1360c 9/22 [58] Field of Search 152/330 R, 357, 361 R,

[56] References Cited UNITED STATES PATENTS 3,554,260 1/1971 Shoemaker 152/361 R 3,559,714 2/1971 Verdier 152/361 DM 3,627,013 12/1971 Chase et a1. 152/361 R 3,669,173 6/1972 Young 152/361 R 3,692,080 9/1972 Boileau.... 152/361 DM 3,717,190 2/1973 Boileau 4 i 152/361 DM 3,757,843 9/1973 Carr t 152/361 DM 3,763,912 10/1973 Bergomi et al. 152/361 DM Primary Examiner-Drayton E. Hoffman Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT 3 Claims, No Drawings PNEUMATIC TllRES The present invention relates to pneumati tires and provides radial tires and bias'belt tires having irii proved properties by using polyester fiber or 6,6-riylon fiber cord layers for the carcass and aromatic polyamide fiber cord layers for the breaker.

The pneumatic tires are classified into the following three kinds in view of the structure.

( l Bias tires wherein the carcass cords and the breaker cords are mutually crossed obliquely against the circumferential direction of the tire.

(2) Radial tires wherein the carcass cords are substantially perpendicular to the circumferential direction of the tire and the breaker cords are substantially parallel to the circumferential direction of the tire.

(3) Bias belt tires wherein the carcass cords are mutually crossed obliquely against the circumferential direction of the tire and the breaker cords are substantially parallel to the circumferential direction of the tire.

The radial tires and the bias belt tires are similar in the structure of the breaker cords and are very superior in the high speed performance, tread wear resistance, cornering performance, ride feeling and fatigue resistance to the bias tires.

The conventional radial tires or bias belt tires use rayon fibers, 6-nylon fibers, 6,6-nylon fibers or polyester fibers as the carcass cords and steel fibers, glass fibers and extremely high modulus rayon (abbreviated as EHM rayon hereinafter) as the breaker cords.

When the rayon cords are used as. the carcass cords, the rayon cords are high in the water absorption, so that the separation and tire breakage are caused early by rain water penetrated from the damage of the side portion 'of tire and 6-nylon fiber cords are very small in the initial modulus and therefore the cornering per formance and the high speed performance are poor.

- On the other hand, when the steel fiber cords are used as the breaker cords, the tread wear resistance and the cornering performance are good but the adhev gn w asrubb li fluot suffiqica tandrtltgbi huspeed performance is poor and particularly the initial modulus of the cords is very high and consequently the ride i 1,1 Z1, J; L l" are poor and the water absorption is high and therefore the early separation and tire breakage are apt to be caused by rain water penetrated from the damage in the tread portion of tires.

The object of the present invention is to provide pneumatic radial or bias tires having improved high speed performance and fatigue resistance and having the same tread wear resistance and cornering performance as the pneumatic tires in which steel fiber cords are used for the breaker and having the same ride feeling as the pneumatic tires in which EHM rayon cords ar e used for the breaker.

The present invention consists in the pneumatic 'tires reinforced with a carcass and a breaker and comprising a tread portion, a pair of side portions extending to both the shoulders of the tread portion and a pair of bead portions formed on each inner periphery of the side portions, characterized in that said carcass is composed of polyester fiber or 6,6-nylon fiber cord layer and said breaker is composed of a layer wherein aromatic polyamide fiber cords having a tenacity of more than l0 g/d, an initial modulus of more than -l g/d,

and a twisting coefficient of cable twist of 0.10 0.60

and that of ply twist of 200 percent based on the cable twist, said twisting coefficient being represented by the following formula,

twist number per 10 cm, D is l/2 of total denier of cord and p is specific gravity of fiber, are embedded in paralfeeling is poor and the cords are rusted by rainwater penetrated from the damage in the tread portion of tires and the tire breakage occurs. When the glass fiber cords are used, the rigidity of the cord is high and therefore the impact absorption is poor and the tread portion is liable to be damaged and the fatigue resistance is inferior to the other fiber cords and when thedeformation is applied locally during running, the cord is fatigued and broken and when an impact is further subjected, the tire breakage is caused. When EHM wherein R R R and R are hydrogen, halogen and hydrocarbon residual.

The aromatic polyamide fiber cords to be used in the present invention have a tenacity of more than 10 g/d,

preferably more than 15 g/d and an initial modulus of i more than g/d, preferably more'than 200 g/d.

When a plurality of aromatic polyamide filaments are twisted to form a cord, if the twisting coefficient is too low, the sizing property of the cord is' considerably poor and the penetration of adhesive is not uniform and the 3 4 cord is apt to be separated from rubber during the run- 1) Test tires ning of tire and the fatigue resistance of the cord is no- Tire A (Present invention): ticcably decreased. While, when the twisting coefii- As the breaker, a layer embedding the cord (a) in a cient is too high, the tenacity and the modulus are conrubber having 300 percent modulus of 150 Kg/cm was siderably decreased. 5 used and as the carcass, polyester fiber cord layer of The twisting coefficient of the cord to be used in the 1,300 d/2 was used. present invention is represented by the following for- Tire B (Present invention): mula As the breaker, a layer embedding the cord (b) in a W, rubber having 300 percent modulus of 180 Kg/cr'n was NT N X XD p X J 10 used and as the carcass, polyester fiber cord of 1,300 wherein NT is a twisting coefficient, N is a number of d/2 was used. twist per 10 cm cord, D is one-half of a total denier of Tire C .(Comparative): the cord and p is a specific gravity of the fiber and the As the breaker, a layer embedding the cord (a) in a twisting coefficient of the cable twist is 0.10 0.60 and rubber having 300 percent modulus of l Kg/cm was the ply twist is 100 200 percent of the cable twist and 15 used and as the carcass, polyester fiber cord of 1,300 the twisting coefficient of the cable twist is preferred to d/2 was used. v be 0.25 0.45. Tire D (Comparative):

When a conventional rubber embedding aromatic As the breaker, a layer embedding the cord (a) in a polyamide fiber cords is used for a breaker wherein the I rubber having 300 percent modulus of 150 Kg/cm was aromatic polyamide fiber cords are arranged in an used and as the carcass, 6-nylon fiber cord of 1,050 d/2 angle of 5 38against-the circumferential direction was used. i of the tire, the tensile modulus is'satisfactorily high but Tire E (Conventional): the bending rigidity is low and the satisfactory tire per- As the breaker, steel cord layer of 1X5 (diameter of formance can not be obtained. Accordingly, a rubber the steel: 0.25 mm) was used and as the carcass, polyeshaving a higher modulus than that of the rubber used ter fiber cord layer of 1,300 d/2 was used.

in the usual synthetic fiber cords is required and has Tire F (Conventional): 300 percent modulus after vulcanization of 130 250 As the breaker, EHM rayon cord layer of 1,650 d/2 Kg/cm preferably 160 250 Kg/cm was used and as the carcass, 6,6-nylon fiber cord layer According to the present invention, it has been found of 1,050 d/2 was used. that the use of the particularly defined cord layers as 2) Test method mentioned above for the carcass and breaker in the ra- Tread wear resistance: dial tires or bias belt tires provides pneumatic tires hav- A road test was effected under the following condiing improved tire performances, particularly, tread tion: wear resistance, cornering performance, ride feeling, Load per 1 tire: about 400 Kg high speed performance and fatigue resistance. Internal pressure of tire: 2.0 Kg/cm The following examples are given for the purpose of Average speed: about Km/hr illustration of this invention and are not intended as Road: Good city road limitations thereof. After 40,000 Km running, the tread wear was measured. EXAMPLE l 40 Cornering performance: As the aromatic polyamide fiber cords to be used in The cornering performance of tire is represented by the pneumatic tires of the present invention, the-cornering force. When a slip angle is given to polyparaphenylene terephthalamide fiber was used for a tire, the car naturally begins to turn and a centrifa breaker and radial tires were prepared as follows and ugal force is'produced by the turning movement. the tread wear resistance, cornering performance, ride The cornering force is a force which is caused by feeling and high speed performance were determined. a frictional force between the tire and the road surface against the centrifugal force in a direction per- Cord (a): I pendicular to the rotating plane of the tire. The tenacity: 13 g/d cornering force is measured by means of a drum initial modulus: 170 g/d tester. twisting coefficient of cable twist: 0.55 The higher cornering force means the better cornertwisting coefficient of ply twist: 0.55 ing performance. I 1,600 d/2 High speed performance:

Cord (b): The high speed performance is measured by running tenacity: 18 g/d a car on a drum tester under a given load-for a initial modulus: 400 g/d given time and then the speed is increased step by twisting coefficient of cable twist: 0.38 step and the speed and time when the tire is brotwisting coefficient of ply twist: 0.38 ken, are measured. 1,600 d/2 Ride feeling: Tire size: The feeling test is made by a test driver.

175-14, 2 ply layers, 3) Test results 7 2 breaker layers The test results are shown in the following Table 1. Angle of carcass cords: The tread wear resistance, cornering performance perpendicular to the circumferential direction of tire and high speed performance are shown by the index based on the measured values of the tire F Angle of breaker cords: (Conventiona1)of 100. The larger index means the 15 against the circumferential direction of tire better property.

Table 1 Test I tire A B C D E F Test Present Present Compar- Compar- Conven- Convenresults invention invention ative ative tional tional Tread wear resistance I45 I50 I25 I20 I55 I Cornering performance I40 I45 I20 I20 I45 I00 Ride feeling Good Good Good Good Bad Good High speed performance I20 I25 I I0 I 95 100 I 'The tires of the present invention have less drawbacks than the conventional tires and are synthetically excellent and particularly the high speed performance is better.

EXAMPLE 2 The aromatic fiber cords used in Example 1 were used for the breaker and the bias belt tires were produced in the following manner and the same test as in Example I was made.

Tire size: C78-l4, 2 ply layers, 2 breaker layers Angle of carcass cord: 32 against the cross sectional direction of tir Angle of breaker cord: 28 against the circumferential direction of tire Tire G (Present invention): 30 As the breaker, a layer embedding the cord (at) in a rubber of 300 percent modulus of I80 Kg/cm was used and as the carcass, 6,6-nylon fiber cord layer of 1,260

d/2 was used.

Tire H (Conventional): WAS- e, s k tc .fih -Lserst lblrLEiEQ-Q; 75-5/0 was used and as the carcass, 6,6-nylon fiber cord of 1,260 d/2 was used.

The test results are shown in the following Table 2.

Table 2 Test tire G H Test results Present invention Conventional Tread wear resistance I35 I00 Cornering performance 150 I00 Ride feeling Good Good High speed performance I40 I00 From the above data it can be seen that the tire of the present invention is synthetically superior to the conventional tire.

What is claimed is:

l. Pneumatic tires reinforced with a carcass and a v breaker and comprising a tread portion, a pair of side portions extending to both the shoulders of the tread portion and a pair of head portions formed on each inner periphery of the side portions, characterized in that said carcass is composed of polyester fiber or 6,6- nylon fiber cord layer and said breaker is composed of a layer wherein aromatic polyamide fiber cords having a tenacity of more than 10 g/d, an initial modulus of more than 150 g/d, and a twisting coefficient of cable twist of 0.10 0.60 and that of ply twist of 200 percent based on the cable twist, said twisting coefficient being represented by the following formula NT= N X V0.l39 D/p X 10 wherein NT represents the twisting coefficient, N is a .twist number per l0 cm, D is one-half of total denier of cord and p is specific gravity of fiber, are embedded in parallel in a rubber having 300 percent modulus of I30 250 Kg/cm and arranged in an angle of 5 38 against the circumferential direction.

2. The pneumatic tires as claimed in claim 1, wherein said aromatic polyamide fiber cords has a tenacity of more than 15 g/d, an initial modulus of more than 200 g/d and a twisting coefficient of the cable twist of 0.25 0.45.

3. The pneumatic tires as claimed in claim 1, wherein the rubber to embed the aromatic polyamide fiber cords has 300 percent modulus of I60 250 Kglcm. 

1. PNEUMATIC TIRES REINFORCED WITH A CARCASS AND A BREAKER AND COMPRISING A TREAD PORTION A PAIR OF SIDE PORTIONS EXTENDING TO BOTH THE SHOULDERS OF THE TREAD PORTION AND A PAIR OF BEAD PORTIONS FORMED ON EACH INNER PERIPHERY OF THE SIDE PORTIONS CHARACTERIZED IN THAT SAID CARCASS IS COMPOSED OF POLYESTER FIBER OR 6,6-NYLON FIBER CORD LAYER AND SAID-BREAKER IS COMPOSED OF A LAYER WHEREIN AROMATIC POLYAMIDE FIBER CORDS HAVING A TENACITY OF MORE THAN 10 G/D, AN INITIAL MODULUS OF MORE THAN 150 G/D, AND A TWISTING COEFFICIENT OF CABLE TWIST OF 0.10 - 0.60 AND THAT OF PLY TWIST OF 100 - 200 PERCENT BASED ON THE CABLE TWIST, SAID TWISTING COEFFICIENT BEING REPRESENTED BY THE FOLLOWING FORMULA
 2. The pneumatic tires as claimed in claim 1, wherein said aromatic polyamide fiber cords has a tenacity of more than 15 g/d, an initial modulus of more than 200 g/d and a twisting coefficient of the cable twist of 0.25 - 0.45.
 3. The pneumatic tires as claimed in claim 1, wherein the rubber to embed the aromatic polyamide fiber cords has 300 percent modulus of 160 - 250 Kg/cm2. 